From those documents, you can see if the stenosis is mentioned in the pre-
surgical report. If so, then a comparison of the pre- and post-
surgical reports should give you an idea of whether it seemed to get better or worse after the surgery.
(3) Was your son's regurgitation due to the coarctation pressure? That, I can't answer at all, because I know so little about COA. It does make sense to me that it could be as you speculate, but I don't know.